Activation of T cells results in the release of Interleukin-2 and the expression of the Interleukin-2 receptor. In humans there are at least two chains that comprise this receptor. In rats there are 4 proteins which can bind IL-2 and together they form the high affinity receptor necessary for the transmission of the IL-2 growth signal. The IL-2 receptor (alpha chain) can be found in soluble form in activated T cell culture supernates, and in serum and CSF from patients with infectious and inflammatory illness. The CSF IL-2R levels are significantly elevated in patients with multiple sclerosis. Influenza vaccine studies have shown additive effects on antibody production with the use of combined parenteral and nasal immunization with killed and live attenuated influenza vaccines.